MAGNETIC PERFORMANCE TRANSITION IN Fe/Tb MULTILAYERS INDUCED BY INTERFACE ROUGHNESS

1. IntroductionIn the past decade, metastable phaJses have been fOund in various multilayers when thedeposited nonequilibrium phases have same crystal structure as the substrate. On suitablesubstrate and under moderate environments it is possible to induce growth of metastablephases. An example is the epitaxial growtli of fcc Fe on fcc Cu substrate where bothelements have close atomic .i...Il'2]. Since the substrate has same crystal structure asthe nonequilibrium phase, the lower interface e…     

Nicalon SiC/Al复合材料中的界面反应

从热力学和动力学方面对Nicalon SiC纤维与Al的化学反应进行了研究,探讨了反应机理及合金元素的影响.实验表明,从953K开始就发生SiC纤维和Al之间的反应.其反应符合抛物线规律;在1013K和1033K反应速率常数分别为3.30×10~(-8)m·s~(-1/2)和3.85×10~(-8)m·s~(-1/2).Mg,Cu和Mn等合金元素的共同作用会加剧其反应.     

INFLUENCE OF THE NONMAGNETIC METAL SPACER ON THE MAGNETIC PROPERTIES AND MICROSTRUCTURE OF THE MULTILAYER FILMS

Ta / NiFe/Bi （ Ag, Cu ）/FeMn/Ta and Ta / NiFe1/FeMn / Bi （ Ag, Cu ）/NiFen/Ta films were prepared by magnetic sputtering. The texture and the dependences of the exchange-coupling field on the thickness of Bi, Ag, and Cu in Ta/NiFe/Bi（Ag, Cu） /FeMn/Ta and Ta/NiFe/FeMn/Bi（Ag, Cu）/NiFe/Ta films were studied. XPS results indicate that the Bi atoms migrated into the FeMn layer during the deposition process and a FeMnBi alloy was probably formed or the Bi atoms existed as an impurity in the FeMn layer in Ta/NiFe/Bi（Ag, Cu ）/FeMn/Ta. Otherwise, in Ta/NiFe/FeMn/Bi （Ag, Cu）/NiFe/Ta films, Bi, Ag, and Cu atoms do not remain entirely at the interface of the FeMn/ NiFeⅡfilm, but at least partly segregate to the surface of the NiFe film.     

退火[Co＼Cu]多层膜的固相反应与磁性

用双对向靶溅射方法制备了两种成分的「Ｃｏ（１．２ｎｍ）／Ｃｕ（ｔＣｕ）」（ｔＣｕ＝１．０ｎｍ，３．４ｎｍ）纳米多层膜。分别用ＴＥＭ和ＴＧ方法研究了「Ｃｏ／Ｃｕ」多层膜结构和磁怀随温度的变化。结果表明：ｔＣｕ＝１．０ｎｍ的多层样品出现了两个磁性转变点，这是因为样品中存在的两种磁性物质。ＴＥＭ分析结果证明这两种铁磁相为ｈｃｐＣｏ－Ｃｕ固溶体。     

磁控溅射Cu/Al多层膜的固相反应

采用磁控溅射技术原子比为2：1、调制周期A分别为20和5nm的Cu/Al多层膜，用X射线衍射（XRD），透射电镜（TEM）和热分析（DSC）等技术研究了多层膜的固相反应。∧＝20nm的多层膜样品中铜和铝膜均沿（III）方向择优生长，加热至145℃时生成α－Cu固溶体，超过191℃时生成γ2-Cu9Al4要。制备态∧＝5nm的样品有α-Cu生成。加热时γ2－Cu9Al4的生成温度显著降低（134℃），测定了∧＝20nm多层膜样品中α-Cu和γ2－CuAl4的形成激活能分别为0．56eV和0.79eV，后者与文献值相符。     

TA2／A3爆炸复合界面的扩散反应

借助于ＯＭ，ＳＥＭ，ＴＥＭ及ＡＥＳ和ＸＲＤ等测试技术和手段，系统地研究和深入探讨了钛（ＴＡ２）／钢（Ａ３）爆炸复合界面扩散反应区内的微观组织结构、反应相的形成和生长规律，结果表明：经１１７３Ｋ以下（即ＴＡ２的β转变温度以下）热处理，在ＴＡ２侧界面形成ＴｉＣ，它阻碍Ｆｅ和Ｔｉ互扩散，不能生成Ｆｅ_（２）Ｔｉ，ＦｅＴｉ．经１２２３Ｋ以上（即在ＴＡ２的β转变温度以上）热处理，沿界面生成按抛物线规律长大的层状金属间化合物（Ｆｅ２Ｔｉ，ＦｅＴｉ）；并由于Ｆｅ的扩散，在ＴＡ２侧Ｆｅ的含量高处形成β－Ｔｉ或β－Ｔｉ＋α－Ｔｉ组织，而在Ｆｅ含量低处形成马氏体转变产物，此外，β转变层也按抛物线规律生长．     

INTERLAYER COUPLING AND FERROMAGNETIC RESONANCE IN Fe-Si/Cr MULTILAYERS

ＩＮＴＥＲＬＡＹＥＲＣＯＵＰＬＩＮＧＡＮＤＦＥＲＲＯＭＡＧＮＥＴＩＣＲＥＳＯＮＡＮＣＥＩＮＦｅ－Ｓｉ／ＣｒＭＵＬＴＩＬＡＹＥＲＳ￥Ｓ．Ｓ．Ｙａｎ：ＹＨＬｉｕ：Ｘ．ＤＭａ,ＹＭ．ＺｈａｎｇａｎｄＬ．ＭＭｅｉ（Ｄｅｐａｒｔｍｅｎｔｏｆｐｈｙｓｉｃｓ,ｓｈ...     

Fe－Dy非晶膜晶化过程中结构及磁性变化

用真空双源蒸镀法在ＮａＣｌ和Ｓｉ单晶衬底上制备Ｆｅ，Ｄｙ成分调制多层膜．研究了非晶膜晶化过程，等温退火后多层膜结构及磁性变化。结果表明，在２００℃以下退火，其沉积态非晶和成分调制结构几乎不变；３００℃开始晶化，首先出现Ｆｅ晶核，随温度升高，Ｆｅ，Ｄｙ逐步晶化，６００℃全部形成晶态ｂｃｃ－Ｆｅ和ｈｃｐ－Ｄｙ．饱和磁化强度Ｍｓ对非晶Ｆｅ，Ｄｙ膜晶化时Ｆｅ晶核的形成十分散感，而只有Ｆｅ晶粒的长大才导致矫顽力Ｈｃ增加．     

Carbon tetrafluoride plasma modification of polyimide: A method of in-situ formed hydrophilic and hydrophobic surfaces

This study demonstrates that carbon tetrafluoride (CF₄) plasma can result in relatively hydrophobic and hydrophilic surfaces formed in-situ on polyimide (PI) films using a mask and controlling the distance of the mask to the substrate. The surface properties of plasma-treated PI films are characterized by contact angle measurement, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Under specific modification conditions, contact angles for hydrophobic and hydrophilic surfaces reach values of 108.3 ± 0.6° and below 5°, respectively. The XPS analyses indicate that the “unshielded” surfaces contained a high proportion of the CF₂-CF₂ group and therefore decreased the wettability of the surface. On the other hand, the “shielded” surface contained hydrophilic groups such as carbonyl or carboxyl with few fluorinated groups, resulting in increased wettability of the surface.     

Sputter deposition and XPS analysis of nickel silicide thin films

Binary component Ni-Si films of different compositions are fabricated on AISI 304L stainless steels by means of ion-beam sputter (IBS) deposition. The compositions of the thin films and the chemical states of elements are analysed by means of X-ray photoelectron spectroscopy (XPS). The phase formation is studied and discussed in view of Pretorius' effective heat of formation (EHF) model. The proportions of the resulting phases can then be deduced. The electronic structure for the various compositions is also qualitatively investigated from the XPS valence band spectra, suggesting the bonding changes from predominating metallic to covalent bonding in Ni-Si systems when Si content increases.     

Effect of varying blends of finished RO, surface and ground waters on solid lead surfaces

PbO, PbCO₃, and Pb₃(OH)₂(CO₃)₂ were identified as primary corrosion products on lead coupons following three months of exposure to finished RO, surface and ground water by XRD and XPS. Based on these results, a Pb₃(OH)₂(CO₃)₂ solid phase equilibrium model was used as a function of water quality, was modified using diffusion theory and accurately predicted lead release for a majority of field observations. SEM photographs revealed sulfate and chloride affected the surface structure of corrosion scales and lead release.     

Surface composition and electrochemical behavior of LiNi1/3Co1/3Mn1/3O2 cathode material with copper additive

LiNi_1/3Co_1/3Mn_1/3O₂（NCM） cathode material containing copper was prepared by co-precipitation method.The material was characterized by X-ray photoelectron spectroscopy（XPS） and galvanostatic cycling.XPS data indicate that surface compositions of the samples containing copper are different from the bare NCM.Copper on surface of particles was enriched,while nickel and lithium content was reduced.The electrochemical performance of NCM was affected by the change of surface compositions.Cycling performance charged to the cutoff voltage of 4.6 V was improved by introducing copper into the material.The effects of copper content on electrochemical behaviors of NCM at 4.5 V were discussed.     

X70管线钢在HCO-3/CO2-3体系中表面膜性能研究

采用动电位扫描和交流阻抗方法研究了X70管线钢在0.5 mol/L Na2CO3+1 mol/L NaHCO3溶液中的阳极极化过程中的电化学行为,通过XPS和SEM对表面膜的组成和形貌进行了分析.结果表明，X70管线钢在阳极极化过程中分别于-600 mV和-350 mV电位处出现2个阳极电流峰；-600 mV时电极表面的反应阻力较小，表面膜主要由FeCO3、Fe2(OH)2CO3和FeOOH等化合物组成，表面膜上存在较多的微孔缺陷，处在一个不稳定状态，表面膜的保护性能较差；-350 mV时电极表面的反应电阻较大, 表面膜主要由铁的氧化物Fe2O3和Fe3O4组成,表面膜具有较好的保护性能.       

用XPS研究钢筋钝化膜和C1~-对钝化膜的影响

采用光电子能谱(XPS)研究钢筋钝化膜的组成与结构,以及氯离子对钝化膜的影响。结果表明,在本实验条件下钢筋钝化膜为双层结构,外层以γ-FeOOH为主,内层主要为FeO;氯离子对胶的破坏过程可能是先在钝化膜表面吸附,然后穿透到膜中,在铁/氧化物界面即膜的内层形成FeCl_2,而使钝化膜局部溶解;复合缓蚀剂的加入使钢筋钝化膜表面γ-FeOOH的含量增大,膜中夹杂一定深度的有机铵盐,硅酸盐只在表面沉积。     

Relationship of Corrosion Behavior Between Single-Phase Equiatomic CoCrNi,CoCrNiFe,CoCrNiFeMn Alloys and Their Constituents in NaCl Solution

The composition is a significant issue for corrosion resistance of metallic materials.To reveal the correlation of corro-sion behavior between multiprinciple alloys and their constituents,a series of single-phase equiatomic alloys of CoCrNi,CoCrNiFe and CoCrNiFeMn was fabricated.The electrochemical and scanning electron microscope results demonstrated that corrosion resistance of the equiatomic alloys in 0.1 M NaCl solution is located in the range but not the average value of their constituents.X-ray photoelectron spectroscopy analysis indicated that the protective performance of passive film is mainly determined by the constituent with the highest corrosion resistance and the breakdown of passive film is mainly dominated by the elements with the highest corrosion rate.Our findings can guide the materials design of multiprinciple alloys with expected corrosion performance.     

MAGNETORESISTANCE EFFECT OBSERVED IN Fe／Mo MULTILAYERS PREPARED BY ELECTRON BEAM EVAPORATION

The Fe/Mo multilayers were prepared by electron beam evaporation, the micro structure and magnetic properties of the multilayers were studied by X-ray diffraction, vibrating-sample magnetometer (VSM) et al. The experimental results revealed that the Fe/Mo multilayers in our experimental conditions behaved magnetoresistance effect with a sharp peak on magnetoresistance (MR) ratio curve, and magnetoresistance is easily saturated at low applied magnetic fields. For [Fe(1.5nm)/Mo(1.0nm)]4,2 multilayers, MR ratio could arrive to 0.1%. The antiferromagnetic interlayer coupling could be observed in some films at room temperature. The strength of the antiferromagnetic interlayer coupling J in the films is low because of the low saturation field Hs. The relationship between magnetic properties and micro structure was also discussed in this paper.     

界面散射对Ni_(80)Co_(20)/M(M=Co,Cr,Ag)多层膜各向异性磁电阻的影响

用磁控溅射方法制备了Ｎｉ８０Ｃｏ２０／Ｍ（Ｍ＝Ｃｏ,Ｃｒ,Ａｇ）多层膜样品系列,Ｃｏ,Ｃｒ,Ａｇ杂质层的标称厚度为０．１ｎｍ,研究了界面散射对多层膜的磁及输运性质的影响．零场电阻率ρ的测量结果表明,对含Ｃｒ样品,ρ随杂质层间距Ｌ的依赖关系能较好的用Ｆｕｃｈｓ－Ｓｏｎｄｈｅｉｍｅｒ（Ｆ－Ｓ）理论描述．而对含Ｃｏ和Ａｇ样品,ρ随Ｌ的依赖关系在Ｌ小于１５ｎｍ时开始偏离Ｆ－Ｓ理论．磁电阻测量表明,含Ｃｒ和Ａｇ样品,各向异性磁电阻Δρ在Ｌ＜１５ｎｍ时随Ｌ的减小陡然下降．对含磁性Ｃｏ元素的样品,其Δρ值在Ｌ＞１５ｎｍ时高于Ｎｉ８０Ｃｏ２０单层薄膜的Δρ值;在Ｌ＜１５ｎｍ时Δρ值随Ｌ呈现振荡变化的趋势．磁性测量表明,三个系列样品的矫顽力Ｈｃ在Ｌ＜１５ｎｍ时都随Ｌ近似直线上升,在Ｌ＞１５ｎｍ后趋于饱和;经４００℃真空退火后Ｈｃ都显著下降．     

不同能量沉积方式对薄膜界面反应的影响

通过分子束外延(MBE)和脉冲激光沉积(PLD)将1～10个Fe原子层(ML)以楔型(wedge-shape)方式分别沉积到NiO(001)基片上,并对其进行磁光克尔效应(MOKE)原位测试.结果表明:通过MBE这种低能量沉积方式沉积的Fe原子层在Fe/NiO界面处产生了约2 ML的磁死层;而通过PLD这种较高能量沉积方式沉积的Fe原子层在Fe/NiO界面处产生了约3 ML的磁死层.X射线光电子能谱(XPS)研究Fe/NiO界面的结果表明:两种沉积方式都能使Fe原子与单晶NiO在界面处发生化学反应,这是导致磁死层的一个重要原因;对于MBE和PLD沉积方式来说,从靶材上被蒸发或溅射下来到达基片的原子所具有的能量很低,分别约为0.1 eV和1.0 eV,反应层较浅;磁控溅射沉积Fe原子的能量约为几～十几电子伏特,导致的反应深度约1.5 nm.     

X射线光电子能谱在材料表面研究中的应用

通过阐述XPS测试原理及工作特点,讨论其在材料表面研究中的具体应用。通过光电子谱峰位置、形状和强度,可以分析元素价态、含量。角分辨XPS可以检测超薄样品表面的化学状态,成像XPS可以显示样品表面的元素和价态分布,从而进行微区分析。利用氩离子刻蚀进行深度剖析,可以研究样品化学状态随深度的变化关系。     

Tantalum oxide barrier in magnetic tunnel junctions

Tantalum as an insulating barrier can take the place of Al in magnetic tunnel junctions (MTJs). Ta barriers in MTJs were fabricated by natural oxidation. X-ray photoelectron spectroscopy (XPS) was used to characterize the oxidation states of Ta barrier. The experimental results show that the chemical state of tantalum is pure Ta~(5+) and the thickness of the oxide is 1.3 nm. The unoxidized Ta in the barrier may chemically reacted with NiFe layer which is usually used in MTJs to form an intermetallic compound, NiTa_2. A magnetic "dead layer" could be produced in the NiFe/Ta interface. The "dead layer" is likely to influence the spinning electron transport and the magnetoresistance effect.